Nucleophilic Germylation of Stable π Bonds via Ge─Ge Bond Heterolysis

Organogermanes have recently attracted a great deal of attention as building blocks for the synthesis of bioactive products, drugs, and functional materials. Metallo-germyls were classically synthesized and employed for nucleophilic germylation to form C─Ge bonds. However, their syntheses require highly reactive organometal reagents, and the scope of germylations involving metallo-germyls is limited due to competition with kinetically favored side reactions. Here, we present a regio/stereo-convergent nucleophilic germylation of stable π bonds by germyl anion generated in situ via heterolytic cleavage of the Ge─Ge bond of digermane (Ge─Ge) in the presence of KO^tBu. This methodology affords unprecedented reactivity, enabling multiple germylation of alkynes and internally selective germylation of alkenes. These reactions are operationally simple, have broad functional group tolerance, and afford densely functionalized aliphatic organogermanes, such as 1-alkyl-1-germylalkanes, 1,1-digermylalkanes, and 1,1,1-trigermylalkanes, without any catalyst.